1. Field of the Invention
This invention relates to a method of cleaning a magnetic recording disk accommodated in a casing to form a magnetic recording disk cartridge.
2. Description of the Prior Art
There has come into wide use as a recording medium for computers floppy disks which are flexible disk of polyester resin or the like having a magnetic layer on each side thereof and on which information is recorded by a magnetic head while the recording disk is rotated.
Recently, there has been put into practice a magnetic recording disk which is smaller than the conventional floppy disks both in thickness and diameter and is generally referred to as a "micro floppy" disk. Generally the micro floppy disk is accommodated in a hard casing to form a cartridge. The micro floppy disk comprises a circular magnetic recording medium which is small in diameter and is thin, and a hub fixed to the center of the recording medium. The hard casing has a hub opening through which the hub is exposed and a magnetic head access opening formed in at least one side wall thereof.
The magnetic recording disk cartridges including the floppy disk and the micro floppy disk are generally provided with a liner on the inner surface of the casing. The liner is formed of an unwoven fabric of rayon or polyester, for example, and is kept in contact with the recording surface of the disk under a light pressure to remove dust on the recording surface while the disk is rotated. The liner has a width at least equal to the width of the recording region of the magnetic recording disk, and is kept pressed against the entire width of the recording surface under a uniform pressure by a lifter which is fixed to the inner surface of the casing at one end and has a resilient arm portion extending obliquely toward the liner to push the liner toward the magnetic recording disk. However, the same amount of information is recorded during one rotation of the disk whether the information is recorded at the outer part or the inner part of the recording region, it follows that as the linear velocity is lower at the inner part than at the outer part, the recording density is higher at the inner part of the recording region than it is at the outer part of the recording region. Therefore, even fine dust particles which may give rise to hardly any problem on the outer part of the recording region can cause drop-out and the like when it deposited on the inner part of the recording region. Accordingly, when the liner is pressed against the recording surface under a uniform pressure that is sufficient for cleaning of the recording surface of the outer part of the recording region, the inner part of the recording region does not receive sufficient cleaning. On the other hand, when the liner is pressed against the recording surface under a higher uniform pressure, the running torque of the recording disk or the torque required to rotate the disk is increased, which is practically undesirable.